java - 为自定义 ListView 设置自定义适配器

Question

我目前正在开发一个项目，该项目将跟踪一款名为 Farkle 的游戏的玩家得分和其他信息。我已经进行了大约 100 次 Google 搜索，并阅读了这里的一些条目。我尝试过实现和使用我发现的一切，但我到这里就结束了。

row.xml 将作为 ListView 中的单个项目加载。

最终，我希望按顺序排列(您将在下面看到我的 row.xml 布局):“玩家姓名”复选框 复选框“玩家得分”。

我可以运行该应用程序，因此在启动时没有出现问题，但是，一旦我尝试添加新播放器，该应用程序就会崩溃。

现在，我下面的代码是一个新项目，因为最后一个项目已经损坏，没有显示任何错误，但在启动时会崩溃。我尝试过使用自定义 ArrayAdapter，我相信这是适合我的方法，但我似乎无法让它在不崩溃的情况下加载 row.xml。我对 ArrayAdapter 还是新手，并且已经完成了一些教程，但仍然无法使其工作。

如果有人对我能做些什么来完成这项工作有任何想法，请帮助并为我指出正确的方向。我已经为此工作了两周了!预先感谢您。

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal" >

    <Button
        android:id="@+id/btnSetScore"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="@string/winning_score" />

    <Button
        android:id="@+id/btnAddPlayer"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/add_player"
        android:textSize="@dimen/activity_horizontal_margin" />

    <Button
        android:id="@+id/btnSetPenalty"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="@string/set_penalty"
        android:textSize="@dimen/activity_horizontal_margin" />

</LinearLayout>

<ListView
    android:id="@+id/lvScoreBoard"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="10"
    tools:listitem="@layout/row" >

</ListView>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal" >

    <Button
        android:id="@+id/btnStatistics"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="@string/statistics" />

    <Button
        android:id="@+id/btnNewGame"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="@string/new_game" />

</LinearLayout>

这是我的row.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

    <TextView
        android:id="@+id/tvPlayer"
        android:layout_weight="4"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="@string/player"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <CheckBox
        android:id="@+id/cbFarkle1"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:enabled="false"
        android:focusable="false"
        android:text="" />

    <CheckBox
        android:id="@+id/cbFarkle2"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:enabled="false"
        android:focusable="false"
        android:text="" />

    <TextView
        android:id="@+id/tvScore"
        android:layout_weight="2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="@string/player_score"
        android:gravity="right"
        android:textAppearance="?android:attr/textAppearanceLarge" />

</LinearLayout>

这是我的MainActivity.java

public class MainActivity extends Activity{

String winningScore = "";
String playerName = "";
String playerScore = "";
String farklePenalty = "";
int penalty;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Creates Buttons
    final Button btnSetScore = (Button) findViewById(R.id.btnSetScore);
    Button btnAddPlayer = (Button) findViewById(R.id.btnAddPlayer);
    final Button btnSetPenalty = (Button) findViewById(R.id.btnSetPenalty);
    Button btnStatistics = (Button) findViewById(R.id.btnStatistics);
    Button btnNewGame = (Button) findViewById(R.id.btnNewGame);

    // Creates ListView for player score board
    final ListView lvScoreBoard = (ListView) findViewById(R.id.lvScoreBoard);

    // Sets the game winning score when the Set Score button is pressed.
    btnSetScore.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO:
            AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
            builder.setTitle("Set Winning Score");

            final EditText input = new EditText(MainActivity.this);
            input.setInputType(InputType.TYPE_CLASS_NUMBER);

            builder.setView(input);

            builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    winningScore = input.getText().toString();
                    btnSetScore.setText(winningScore);
                    InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                    imm.toggleSoftInput(InputMethodManager.HIDE_NOT_ALWAYS, 0);
                }
            });

            builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {    
                    dialog.cancel();        
                    InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                    imm.toggleSoftInput(InputMethodManager.HIDE_NOT_ALWAYS, 0);
                }

            });

            builder.show();

            InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
            imm.toggleSoftInput(InputMethodManager.SHOW_FORCED, 0);

        }
    });

    // Adds a new player to the game when Add Player button is pressed.
    btnAddPlayer.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
            builder.setTitle("Add Player");

            final EditText input = new EditText(MainActivity.this);
            input.setInputType(InputType.TYPE_CLASS_TEXT);

            builder.setView(input);

            builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    playerName = input.getText().toString();



                    InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                    imm.toggleSoftInput(InputMethodManager.HIDE_NOT_ALWAYS, 0);
                }
            });

            builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {    
                    dialog.cancel();        
                    InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                    imm.toggleSoftInput(InputMethodManager.HIDE_NOT_ALWAYS, 0);
                }

            });

            builder.show();

            InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
            imm.toggleSoftInput(InputMethodManager.SHOW_FORCED, 0);

        }
    });

    // Sets the third farkle penalty when Set Penalty button is pressed.
    btnSetPenalty.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
            builder.setTitle("Set Farkle Penalty");

            final EditText input = new EditText(MainActivity.this);
            input.setInputType(InputType.TYPE_CLASS_NUMBER);

            builder.setView(input);

            builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    farklePenalty = input.getText().toString();
                    penalty = Integer.parseInt(input.getText().toString());
                    btnSetPenalty.setText(farklePenalty);
                    InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                    imm.toggleSoftInput(InputMethodManager.HIDE_NOT_ALWAYS, 0);
                }
            });

            builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {    
                    dialog.cancel();        
                    InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                    imm.toggleSoftInput(InputMethodManager.HIDE_NOT_ALWAYS, 0);
                }

            });

            builder.show();

            InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
            imm.toggleSoftInput(InputMethodManager.SHOW_FORCED, 0);

        }
    });

    // Changes to statistics activity when Statistics button is pressed.
    btnStatistics.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

        }

    });

    // Resets all data when New Game button is pressed.
    // This will also have the ability to keep player names, 
    // but erase farkle counts, player scores, penalty, 
    // and winning score.
    btnNewGame.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

}

自定义ListAdapter，但我知道这是错误的。

public class GeneralAdapter extends BaseAdapter {

private static final CharSequence Name = null;
private LayoutInflater mInflater = null;
private ArrayList<String> info = null;

public GeneralAdapter( ArrayList<String> info) {
    this.info = info;
}

String name;
String score = "0";
boolean farkle1 = false;
boolean farkle2 = false;

@Override
public int getCount() {
    return info.size();
}

@Override
public Object getItem(int position) {
    return info.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder;

    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.row, null);

        holder = new ViewHolder();
        holder.generalTV = (TextView) convertView.findViewById(R.id.tvPlayer);
        holder.generalCB = (CheckBox) convertView.findViewById(R.id.cbFarkle1);
        holder.generalCB2 = (CheckBox) convertView.findViewById(R.id.cbFarkle2);
        holder.generalTV2 = (TextView) convertView.findViewById(R.id.tvScore);

        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    holder.generalTV.setText(name);
    holder.generalCB.setChecked(farkle1);
    holder.generalCB2.setChecked(farkle2);
    holder.generalTV2.setText(score);

    return null;
}

private class ViewHolder {
    TextView generalTV;
    TextView generalTV2;
    CheckBox generalCB;
    CheckBox generalCB2;
}

}

Answer 1

崩溃日志或至少您遇到的异常会有所帮助。

也就是说，我可以看到一个问题。您从 getView() 返回 null。尝试返回convertView:

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder;

    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.row, null);

        holder = new ViewHolder();
        holder.generalTV = (TextView) convertView.findViewById(R.id.tvPlayer);
        holder.generalCB = (CheckBox) convertView.findViewById(R.id.cbFarkle1);
        holder.generalCB2 = (CheckBox) convertView.findViewById(R.id.cbFarkle2);
        holder.generalTV2 = (TextView) convertView.findViewById(R.id.tvScore);

        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    holder.generalTV.setText(name);
    holder.generalCB.setChecked(farkle1);
    holder.generalCB2.setChecked(farkle2);
    holder.generalTV2.setText(score);

    return convertView;  // HERE!!
}

此外，当您从 ConvertView 中获取 Holder 时，您可能需要进行一些空检查。如果由于某种原因，最终结果为 null，那么从中引用的第一个内容将导致 NRE。我看不出您的代码有任何问题，但由于您遇到了崩溃，因此值得一试。

<小时/>

退一步来说，您永远不会使用适配器内的信息。换句话说，每个列表项看起来都完全相同，因为它们使用相同的值(名称、farkle1、farkle2、分数)。

也许您的意思是拥有一个包含这些成员的对象数组？像这样:

public class DataItem {
    String name;
    String score = "0";
    boolean farkle1 = false;
    boolean farkle2 = false;
}

然后将其传递到您的适配器中，如下所示..(注意:我还没有尝试编译)

public class GeneralAdapter extends BaseAdapter {

private static final CharSequence Name = null;
private LayoutInflater mInflater = null;
private ArrayList<DataItem> info = null;

public GeneralAdapter( ArrayList<DataItem> info) {
    this.info = info;
}

@Override
public int getCount() {
    return info.size();
}

@Override
public Object getItem(int position) {
    return info.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder;
    DataItem dataItem = getItem(position);

    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.row, null);

        holder = new ViewHolder();
        holder.generalTV = (TextView) convertView.findViewById(R.id.tvPlayer);
        holder.generalCB = (CheckBox) convertView.findViewById(R.id.cbFarkle1);
        holder.generalCB2 = (CheckBox) convertView.findViewById(R.id.cbFarkle2);
        holder.generalTV2 = (TextView) convertView.findViewById(R.id.tvScore);

        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    holder.generalTV.setText(dataItem.name);
    holder.generalCB.setChecked(dataItem.farkle1);
    holder.generalCB2.setChecked(dataItem.farkle2);
    holder.generalTV2.setText(dataItem.score);

    return convertView;
}

private class ViewHolder {
    TextView generalTV;
    TextView generalTV2;
    CheckBox generalCB;
    CheckBox generalCB2;
}
}

顺便说一句，这基本上是一个 ArrayAdapter，您可以轻松地使用它。